I'm not quite sure I'm following all of this myself.
If the tails are 120mm and it is TN-C-S then Table 54.8 gives 35mm for the main bonds - that seems fine. Are the service pipes bonded from the incomer, or from the various DB at the ends of the sub-mains?
However, assuming the SWA is 4-core than it would be met a 95mm from the linked table on the basis of adiabatic equivalence. However, for PME fault currents of a long duration I was imagining you would look at the approximation of steel being around 8 times copper for the same CCC and that is where @westward10 is getting the 240mm SWA from (e.g. Prysmian table has 4-core 240mm SWA having 289mm of steel so about 36mm copper equivalent).
Outside of the PME fault case, the issue for the SWA armour would be more end of circuit Zs and the adiabatic for the OCPD at the source (assuming it is not directly off 120mm tails - please tell me they have not been that stupid?)
So definitely main bonds need upgraded to 35mm.
Not so obvious is if the SWA is OK and that would depend on meeting sub-main Zs for disconnection times and the adiabatic (we would like to think this was done originally, even if the TN-C-S requirements are more recent) AND if they are also bonded to extraneous parts.
If 'also' then would the SWA armour only need to meet the 16mm of Table 54.8? If so it is still looking at 120mm so not met on existing cables and then it would be down to the real nature of bonding at sub-boards and then to decide if added CPC can be run in. TT'ing them is always a possible idea, but not likely to be a better idea!
If the tails are 120mm and it is TN-C-S then Table 54.8 gives 35mm for the main bonds - that seems fine. Are the service pipes bonded from the incomer, or from the various DB at the ends of the sub-mains?
However, assuming the SWA is 4-core than it would be met a 95mm from the linked table on the basis of adiabatic equivalence. However, for PME fault currents of a long duration I was imagining you would look at the approximation of steel being around 8 times copper for the same CCC and that is where @westward10 is getting the 240mm SWA from (e.g. Prysmian table has 4-core 240mm SWA having 289mm of steel so about 36mm copper equivalent).
Outside of the PME fault case, the issue for the SWA armour would be more end of circuit Zs and the adiabatic for the OCPD at the source (assuming it is not directly off 120mm tails - please tell me they have not been that stupid?)
So definitely main bonds need upgraded to 35mm.
Not so obvious is if the SWA is OK and that would depend on meeting sub-main Zs for disconnection times and the adiabatic (we would like to think this was done originally, even if the TN-C-S requirements are more recent) AND if they are also bonded to extraneous parts.
If 'also' then would the SWA armour only need to meet the 16mm of Table 54.8? If so it is still looking at 120mm so not met on existing cables and then it would be down to the real nature of bonding at sub-boards and then to decide if added CPC can be run in. TT'ing them is always a possible idea, but not likely to be a better idea!